Geographic Range

Silurus glanis, sheatfish or wels catfish, is native to eastern Europe and Asia. It has been introduced to several other areas including Germany, France, Spain, England, Greece, Turkey and the Netherlands. (Black, Predator-fishing.co.uk 2005)

Physical Description

The elongated, scaleless body has a strong upper body and a laterally flattened tail. Silurus glanis varies in color. The upper side is usually a dark color and the flanks and belly are more pale. The fins are brownish. The body has a mottled appearance that is sometimes accompanied by brown spots. These catfish can grow to be quite large, perhaps as large as 3 meters long. A maximum reported weight was 220 kg. Most individuals reach sizes between 1.3 and 1.6 meters. Silurus glanis reach an average of 45 kg and has been considered one of the largest freshwater fish in its range.

Reproduction

The male creates a shallow depression that will hold thousands of eggs laid by the female. The eggs are protected by the male until they hatch. Females can lay about 30,000 eggs per kilogram of body weight. Males grow faster and mature earlier than females. One study found that males matured at 78.82 cm at age 3 and females matured at 87.05 cm at age 4. (Black, Predator-fishing.co.uk 2005)

Behavior

Silurus glanis is a solitary species that prefers still waters, usually with a soft bottom like mud. They may live in river bed holes under overhangs of banks, or under other obstructions on river or lake beds such as sunken trees. These fish are most active at night and can tolerate brackish water. (Kirsten Pohlmann, et al., 2001)

Home Range

Nothing is known about home range sizes or patterns of movement in these catfish.

Communication and Perception

Silurus glanis individuals use their barbels and olfactory buds to sense chemical cues in the water. They are thought to be extraordinarily sensitive to chemical stimuli. They also have a lateral line system that helps them detect water movement.
Silurus glanis individuals may use path analysis to track prey. One study found that S. glanis can track the three-dimensional swim path of a guppy and successfully attack it without the presence of light. Little is known about communication in these mainly solitary animals. (Bridgeman, Predator-fishing.co.uk 2005)

Food Habits

Silurus glanis fry feed on plankton during their first year of life. When they reach larger sizes they begin to eat worms, snails, crustaceans, aquatic insects, and small fish. At adult sizes they will also prey on ducks, voles, crayfish, fish, eels, frogs, rats, coypu, and snakes. They use the incredible suction created by suddenly opening their large mouths to take in prey.

Both the top and bottom jaws each have hundreds of inward sloping, soft teeth used to grip prey. There are two "crushing plates" in front of the throat cavity used to crush prey before swallowing. Silurus glanis manipulate their prey prior to consumption by using several short spikes along the edge of the gill rakers. (Black, Predator-fishing.co.uk 2005)

Predation

Northern pike (Esox lucius) and humans are two predators of Silurus glanis. Their large size protects adults from many predators. Smaller fish may be protected somewhat by their dorsal spines. (Froese and Pauly, 2005)

Ecosystem Roles

Silurus glanis carry bacterial diseases that can be transmitted to other fish. They are important predators of fish, crustaceans, small mammals, and aquatic birds. (Farkas and Szitóné, 1986; Farkas, 1985)

Commensal/Parasitic Species

"red head disease" (Vibrio sp. bacterium)

"gill disease" (Flavobacterium)

Economic Importance for Humans: Positive

Silurus glanis is a commercial fish consumed by humans. This fish has boneless white flesh that is low in fat and highly palatable. Technological research for artificial reproduction, population genetics and conservation problems have been developed over the past 10 years in the Czech Republic, France and other European countries.
It is also a valued game fish in European countries. (Froese and Pauly, 2005; Linhart, et al., 2002)

Economic Importance for Humans: Negative

Silurus glanis introductions have been implicated in declining populations of other commercial fishes. (Froese and Pauly, 2005)

Conservation Status

Silurus glanis populations appear to be stable. They are protected by Appendix III of the Bern Convention. In areas where these fish have been introduced, negative ecological consequences have been noted. (Froese and Pauly, 2005)

Contributors

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

Kirsten Pohlmann, , Frank W. Grasso, Thomas Breithaupt. 2001. Tracking wakes: The nocturnal predatory strategy of piscivorous catfish. Proceedings of the National Academy of Sciences of the United States of America, June 19; 98(13): 7371–7374.
Accessed
October 31, 2005
at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=34675.

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.